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Diffstat (limited to 'libgo/go/strings/strings_s390x.go')
-rw-r--r-- | libgo/go/strings/strings_s390x.go | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/libgo/go/strings/strings_s390x.go b/libgo/go/strings/strings_s390x.go new file mode 100644 index 0000000000..b47702fd51 --- /dev/null +++ b/libgo/go/strings/strings_s390x.go @@ -0,0 +1,100 @@ +// Copyright 2016 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// +build ignore + +package strings + +//go:noescape + +// indexShortStr returns the index of the first instance of sep in s, +// or -1 if sep is not present in s. +// indexShortStr requires 2 <= len(sep) <= shortStringLen +func indexShortStr(s, sep string) int // ../runtime/asm_$GOARCH.s + +// supportsVX reports whether the vector facility is available. +// indexShortStr must not be called if the vector facility is not +// available. +func supportsVX() bool // ../runtime/asm_s390x.s + +var shortStringLen = -1 + +func init() { + if supportsVX() { + shortStringLen = 64 + } +} + +// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s. +func Index(s, sep string) int { + n := len(sep) + switch { + case n == 0: + return 0 + case n == 1: + return IndexByte(s, sep[0]) + case n == len(s): + if sep == s { + return 0 + } + return -1 + case n > len(s): + return -1 + case n <= shortStringLen: + // Use brute force when s and sep both are small + if len(s) <= 64 { + return indexShortStr(s, sep) + } + c := sep[0] + i := 0 + t := s[:len(s)-n+1] + fails := 0 + for i < len(t) { + if t[i] != c { + // IndexByte skips 16/32 bytes per iteration, + // so it's faster than indexShortStr. + o := IndexByte(t[i:], c) + if o < 0 { + return -1 + } + i += o + } + if s[i:i+n] == sep { + return i + } + fails++ + i++ + // Switch to indexShortStr when IndexByte produces too many false positives. + // Too many means more that 1 error per 8 characters. + // Allow some errors in the beginning. + if fails > (i+16)/8 { + r := indexShortStr(s[i:], sep) + if r >= 0 { + return r + i + } + return -1 + } + } + return -1 + } + // Rabin-Karp search + hashsep, pow := hashStr(sep) + var h uint32 + for i := 0; i < n; i++ { + h = h*primeRK + uint32(s[i]) + } + if h == hashsep && s[:n] == sep { + return 0 + } + for i := n; i < len(s); { + h *= primeRK + h += uint32(s[i]) + h -= pow * uint32(s[i-n]) + i++ + if h == hashsep && s[i-n:i] == sep { + return i - n + } + } + return -1 +} |